Several categories of experiments on monkeys are planned with the broad goal of better understanding the organization, development, and injury related plasticity of sensory and motor systems in humans. (1) Normal organization and connection patterns will be investigated at cortical, brainstem, and spinal cord levels with the use of microelectrode mapping methods, single unit recordings, and a range of anatomical tracers. This information is basic for understandings of how complex sensory systems of higher primates process information and produce motor patterns. The results also serve as a comparison and control for investigation of injury induced plasticity in adult and developing systems. (2) Limited studies on the normal development of cortical sensory representations and connections will use the same methods, and will be important in both understanding normal development and how injury to developing systems can alter development. (3) A major part of the research program will be directed toward understanding how adult and developing somatosensory systems reorganize as a result of peripheral nerve injury with and without regeneration. Cortical representations of the hand will be studied for alterations from normal organization with microelectrode mapping methods, and the condition of regenerated and adjacent intact nerves will be evaluated independently with anatomical tracing methods. The results will have major implications for understanding of the consequences of nerve and brain injury in adult and developing humans, and should provide information relevant to repair and treatment strategies. In addition, the results will be important in constructing and revising theories of how the nervous system develops and self-organizes.